Optical Power Sensor

[random person]

Was trying to build my own laser power meter but I can't seem to figure out where people buy their sensors or what is the proper verbiage behind the sensors used in a laser power meter. The ones that are stocked are too expensive and have features i'm not super interested in. Where as the cheaper ones are generally sold out. Soo... i'd like to build my own.

I'm a EE hobbyist so the logistics behind powering and displaying the data wouldn't be too hard for me. I'm just kinda at a dead end if I can't get a sensor. I highly doubt this is the type of thing you "extract". Its also of no safety concern so I wouldn't think its highly regulated by governments such as the diodes. Thus I assume one should be able to find it on a site like Electronic Components Distributor | DigiKey Corp. | US Home Page or Mouser Electronics - Electronic Component Distributor right? Anyone got any ideas? Would greatly appreciate it. =)

If someone were to contribute i'd be fully willing to make a very nice detailed walkthrough on how to build your own

 

[Bluefan]

Are you looking for a thermal or photoelectric power sensor?

 

[random person]

Which ever works with a decent degree of accuracy? Not sure what laserbee and radiant alpha use. I'd like to build a meter equivalent to one of those. I got a pic board+microprocessor + power source... again, I just need a sensor that has a good degree of accuracy and can be bought off of a common electronics dealer such as digikey or mouser.

 

[lasersbee]

Was trying to build my own laser power meter but I can't seem to figure out where people buy their sensors or what is the proper verbiage behind the sensors used in a laser power meter. The ones that are stocked are too expensive and have features i'm not super interested in. Where as the cheaper ones are generally sold out. Soo... i'd like to build my own.

I'm a EE hobbyist so the logistics behind powering and displaying the data wouldn't be too hard for me. I'm just kinda at a dead end if I can't get a sensor. I highly doubt this is the type of thing you "extract". Its also of no safety concern so I wouldn't think its highly regulated by governments such as the diodes. Thus I assume one should be able to find it on a site like Electronic Components Distributor | DigiKey Corp. | US Home Page or Mouser Electronics - Electronic Component Distributor right? Anyone got any ideas? Would greatly appreciate it. =)

If someone were to contribute i'd be fully willing to make a very nice detailed walkthrough on how to build your own

You don't seem to be aware of one problem with building
your own LPM... It always comes back to this...
You need to calibrate your DIY LPM against a know good
calibrated Laser Power Meter...

You can get an idea of the wind speed by sticking a wet
finger into the air... but you will never know the true
wind speed unless you have a calibrated Anemometer..


Jerry

 

[laser_freak]

Generally thermal sensors are more accurate as optical sensors' output varies with wavelength. Unfortunately there is not a large market for such thermal sensors and therefore they are not readily sold by distributors such as Digikey. The sensors used in the lasersbee and radiant alpha are nothing more than thermoelectric coolers used in reverse, and an opamp to amplify their output. They are painted black to absorb more of a laser's radiation, and the opposite side is attached to a heatsink to adjust for ambient temperature. A good overview of how to construct such a sensor can be found in this thread: http://laserpointerforums.com/f42/diy-thermal-lpm-under-50-a-51129.html
The major downside is that you need an existing laser power meter in order to calibrate the output from the opamp. Very similar to the chicken or the egg paradox. You may be able to find a member willing to calibrate yours for you.

The other option for thermal sensors are thermopiles. They are used in professorial, lab grade meters from Ophir, Coherent, etc... Every once in a while a large batch of quality ones pop up on ebay. The current thermopiles circulating the hobbiest market are the OPHIR 20C-A thermopiles and can be found in this hobbyist meter: http://laserpointerforums.com/f64/5-watt-laser-power-meter-50226.html
Unfortunately all of the members who originally bought the batch from ebay are not willing to sell just the sensor, and instead insist on selling a complete meter for much more money.

If you can find a thermopile, I suggest you use it. They usually output 1mV per 1mW of optical input. Although it is best to calibrate them, it is not necessary.